Of the total weight of fresh compost used at the start of growing, about half is left at the end. The casing soil with which the compost is cased is not removed separately after harvesting. The whole growing layer is removed and is known by the name of spent mushroom compost or organic compost. The product is also called “champost”.

Spent mushroom manure is used for many fertilizing purposes and is thus regularly analyzed. Nothing is said here about the fertilizing value of spent mushroom compost or about the effectiveness of the various elements, since these can vary depending on crop and type of soil. This can be examined better by specialized fertilizer experts for each individual case.

In general, spent compost is regarded as an attractive material for improving soil texture. It contains much of organic matter, few heavy metals, and no weed seeds or pathogens which are harmful to agriculture or horticulture.

The high lime and salt contents must be taken into account when it is being used. Calcium is usually found in the form of CaCO 3 (70% from the sugar beet factory waste lime in the casing soil), but also as CaSO 3 (20% from gypsum in the compost), while the remainder comes from straw and manure. Calcium can cause a problem if spent compost is used in crops needing a low pH. The soluble salt can give rise to a problem in soils already high in salt content, or in crops which are sensitive to salt. The risk of these problems is greater in glasshouses than in crops in the open ground. This difference is due in particular to the fact that lower quantities are used in the open ground, and the leaching out is greater there.

Ammonia damage is sometimes found, particularly if spent compost is used for seedlings, young plants or in higher amount. The problem can be avoided by not using mushroom compost which is too fresh.

Spent mushroom substrate/ organic compost was earlier regarded as useless waste but recent researches have shown that it has many usages for organic farming. SMS has also been recommended for use in purification of contaminated soils and also in the reclamation and improvement of soil health.

I hope in the middle east where there is so much of sarcity of plant growth substraight, this product will find its own place.